This invention relates to ion sources and especially to an ion source utilizing a charge exchange process to change a molecular beam to an ion beam.
Ion beam sources have found various applications, one being in the fabrication of integrated circuits. Integrated circuit fabrication is now beginning a new phase. A few years ago, the goal was the fabrication of very large scale integrated circuits (VLSI) in which as many functions as possible were crowded on one chip. Now there is a drive to develop very high speed integrated circuits (VHSIC), in which the objective is to increase speed by shrinking components to submicron dimensions. For the initial stages of VHSIC work, electron beam microlithography is being used.
The objective of particle beam lithography is to write a pattern on a semiconductor surface with a tiny focused spot of charged particles. This pattern can then be treated to form an integrated circuit. Essential to this process is the source of the charged particles; the closer it is to being an ideal monochromatic point source, the smaller the final spot size can be. Also, the more current the source produces, the faster the pattern can be written. A means is described herein which constitutes such a nearly ideal ion source, superior to any previous charged particle source intended for microlithography.
Ions have an advantage over electrons in being approximately one hundred times more effective at exposing resist material used in chip fabrication. This would reduce the cost/wafer/hour for an ion beam of the same current and spot size as an electron beam.
Another advantage of ions over electrons is that much greater resolution is possible, due to the absence of backscattering by the substrate (the proximity effect).
Ions also permit entirely new techniques to be used. SiO.sub.2 can be exposed directly, without first exposing a layer of resist. Etching of SiO.sub.2 by sputtering could be done directly and this step could be followed immediately by implantation within the same vacuum chamber.